We are investigating approaches for utilizing recombinant DNA techniques in developing a vaccine for human respiratory syncytial virus (RSV). Previously, vaccinia virus recombinants that express individually the RSV F and G glycoproteins were shown to be highly immunogenic and effective in inducing resistance to challenge RSV infection in rodents and non-human primates. Analogous recombinants are being constructed with vaccinia virus strains (Wyeth and Lister) that are acceptable for sue in humans. Vaccinia virus recombinants also have been constructed with seven other RSV genes, namely the 1C, 1B,N, P, M 22K and 1A genes. Expression of the authentic RSV protein has been confirmed in each case, and these recombinants are being used to evaluate possible roles for these proteins in host immunity and virus-induced pathology. Two different adenovirus type 5 recombinants that contain the RSV F gene under the control of adenovirus promoters have been constructed, and these are being analyzed to determine whether the F protein is synthesized and processed authentically in recombinant-infected cells. Recombinant baculoviruses that express individually the F and G proteins are being evaluated as a potential source of purified F and G protein for a non-replicating subunit vaccine.